The Cambrian Explosion generally refers to the geologically sudden appearance of complex organisms on earth in antiquity.

What is striking is that the geologic record immediately preceding this period is largely devoid of complex organisms.

Some call the Cambrian explosion the "evolutionary big bang," because (the claim goes) life evolved at rates of over twenty times the Precambrian rate. From approximately 535 million years ago to 520 million years ago, nearly all the animal phyla in existence today first appeared in the fossil record.

Question #3 Given the large numbers of species in the fossil record extant in Cambrian fossil beds, explain why fossil beds beneath them are devoid of transitional fossils? What mechanism was responsible for this vast array of species suddenly appearing in the fossil record?